Researchers from Australia and Qatar analysed 69,990 middle‐aged and older adults, to investigate if individual dietary supplements were related to the incidence of CVD, obesity, or both as well as if the joint effects of long‐term diet and dietary supplements were related to the incidence of CVD, obesity, or both.
MVM, fish oil, and calcium supplements were examined in this study as they were the most commonly used within the Australian population, and “they are the most controversial in terms of the relationship to disease outcomes,” researchers wrote in the Nutrients journal.
The participants were part of the 45 and Up Study (n=267,153) conducted between 2006 to 2009 (baseline), with a follow-up survey from 2012 to 2015.
The selected 69,990 participants were aged 45 and above, who completed both baseline and follow-up questionnaires.
Participants were identified as having CVD if they had physician diagnosis, stroke or recent treatment. Obesity was calculated using BMI.
Dietary consumption was assessed using short food frequency questions, where points were given for meeting the adequate fruit and vegetable intake, as well as lean meat, poultry, seafood, dairy and alcohol consumption.
Diets were scored from healthiest to the least healthy behaviour.
For dietary supplements, MVM, fish oil, omega‐3, and calcium frequency and consumption were analysed using a questionnaire.
Over the course of the study, obesity rate rose from 26.9% to 35.2%.
CVD rates also grew from 15.6% at baseline to 29.2% at follow-up.
For comorbid obesity and CVD, rates also increased from 5.6% to 12%.
It was observed that supplementation with MVM, fish oil, and calcium were associated to lower risk of obesity (IFF: 0.97, 0.96, 0.94 respectively). IFF is incidence rate ratio. The reference is 1.0.
This meant that calcium supplementation had the lowest incidence of obesity compared to MVM or fish oil.
Supplementation with MVM and fish oil were also associated to lower incidence of CVD (IFF: 0.81, 0.89 respectively), but not calcium (IFF: 1.07).
Supplementation with MVM, fish oil, and calcium resulted in lower incidence of CVD and obesity combined (IFF: 0.69, 0.75, 0.94 respectively). The higher figure for calcium here could be due to its CVD association shown earlier.
Healthy vs unhealthy diet
When researchers analysed the joint effects of a healthy diet versus unhealthy diet and consumption of dietary supplements in relation to the incidence of CVD and obesity combined, they found that people with a healthy diet and long-term MVM use had the lowest incidence (IRR: 0.49).
People with a healthy diet and were new MVM consumers also had a lower incidence (IFF: 0.88), while those with a healthy diet and were former users of MVM actually had a higher incidence (IFF: 1.11).
In the unhealthy diet group, those not consuming MVM or were former users had higher incidence (IFF: 1.11) of getting CVD and obesity together. Those newly converted users of MVM and long-term users despite their unhealthy diets had lower incidence (IFF: 0.88, 0.62 respectively).
For fish oil, people with a healthy diet and were new users of fish oil as well as long-term users had IFF of 0.68 and 0.64 respectively. Those with a healthy diet and were former fish oil users had IFF of 0.98.
People with unhealthy diets and were new and former fish oil users recorded IFFs of 0.91 and 0.85 respectively. Non-users had increased risk (IFF: 1.06).
Those with an unhealthy diet, yet were long-term users of fish oil had lower incidence too (IFF: 0.63).
For calcium, the lowest risk was found in people with a healthy diet and were former calcium users (IFF: 0.58), followed by long-term calcium users (IFF: 0.78), and new calcium users (IFF: 0.91).
In the unhealthy diet, people with former and long-term calcium use had an IFF of 0.60 and 0.61 respectively. Non-users and new users of calcium reported increased risk of 1.08 and 1.18 respectively.
Through these findings, it suggests that participants who maintained a long-term healthy diet, combined with multivitamins and minerals or fish oil supplements, had a lower incidence of CVD and obesity than those not taking supplements.
Researchers pointed out that calcium supplementation combined with a healthy diet in lowering the risk of obesity in middle‐aged and older people, which may propose a potential strategy for obesity prevention.
“The possible biological mechanisms underlying the effects of calcium on obesity include regulation of adipogenesis, modulation of fat metabolism, promotion of adipocyte proliferation and apoptosis, enhancement of thermogenesis, suppression of fat absorption and promotion of fecal fat excretion, and modification of gut microbiota composition,” they explained.
While this study provided comprehensive data from its large population sample, it had several limitations.
In the questionnaire, participants were only asked if they had taken supplements in the past four weeks, so dosages were unknown, and they may have under‐ or overestimated results of the association.
“Our study was also unable to distinguish specific vitamins which may have potential benefits such as vitamin D against CVD and obesity, since vitamins were clustered under multivitamins and minerals in the survey.”
Researchers recommend that further large scale and longitudinal epidemiological studies in examining the joint effect of diet and supplements be conducted.
“The Joint Effects of Diet and Dietary Supplements in Relation to Obesity and Cardiovascular Disease over a 10-Year Follow-Up: A Longitudinal Study of 69,990 Participants in Australia”
Authors: Xiaoyue Xu, et al.